Filling elements and filling machines for filling bottles or similar containers, in particular also for pressure-filling, are known in different embodiments.
For the purpose of the invention, the term “pressure-filling” is to be understood generally to mean a filling method wherein before the actual filling phase, i.e. before the opening of the liquid valve, the respective container that is to be filled and that lies with its container mouth in sealed position against the filling element is pre-stressed with a pressurised pressure gas (inert gas or CO2 gas) which the filling material flowing to the container then increasingly displaces as return gas from the container interior during filling.
For the purpose of the invention, “container in sealed position with the filling element” means that the respective container that is to be filled lies in the manner known to the skilled person with its container mouth pressed seal-tight against the filling element or against a seal at that location which encircles the at least one discharge port.
In the case of known filling elements, the pressure gas is delivered to the respective container and the return gas is taken away from the respective container over one and the same controlled gas path configured in the filling element, i.e. over a gas path in which a control valve is disposed. This is then for example part of a pneumatic control valve array and is controlled by at least one electrically controllable switching valve of a machine controller of the filling machine.
In order among other things to increase the output of a filling machine (number of filled containers per unit of time) while maintaining the gentle filling of the containers, it would make sense if the effective flow cross-section of the gas path for the pressure gas were greater than the effective flow cross-section of the gas path for the return gas, since on the one hand the time (cycle time) for pre-stressing can be reduced and on the other hand a filling speed that is optimum for gentle filling can be achieved in this way. For the purpose of the invention, “effective flow cross-section” means that flow cross-section which the respective gas path exhibits overall and which is essentially determined by the section (gas path section) of the gas path having the smallest cross-section.
This requirement for a larger effective flow cross-section for the pressure gas and at the same time for a reduced effective flow cross-section for the return gas cannot be satisfied by a single control valve in the common gas path for the pressure gas and the return gas.
Instead this would require at least two control valves with associated electrical switching valve, and this would mean a considerable complexity in terms of both design and in particular of circuit engineering and control engineering.